Semiconductor device with contamination improvement

ABSTRACT

A semiconductor device includes a substrate, two gate structures, an interlayer dielectric layer and a material layer. The substrate has at least two device regions separated by at least one isolation structure disposed in the substrate. Each device region includes two doped regions in the substrate. The gate structures are respectively disposed on the device regions. In each device region, the doped regions are respectively disposed at two opposite sides of the gate structure. The interlayer dielectric layer is disposed over the substrate and peripherally surrounds the gate structures. A top of the interlayer dielectric layer has at least one concave. The material layer fills the concave and has a top surface elevated at the same level with top surfaces of the gate structures. A ratio of a thickness of a thickest portion of the material layer to a pitch of the gate structures ranges from 1/30 to 1/80.

PRIORITY CLAIM AND CROSS-REFERENCE

This is a divisional application of U.S. patent application Ser. No.14/839,932 filed on Aug. 29, 2015, which is incorporated herein byreference in its entirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. In the course of the IC evolution, functional density (definedas the number of interconnected devices per chip area) has generallyincreased while geometry size (i. e., the smallest component (or line)that can be created using a fabrication process) has decreased. Ascaling down process generally provides benefits by increasingproduction efficiency and lowering associated costs. But, such scalingdown has increased the complexity of processing and manufacturing ICs.For these advances to be realized, similar developments in ICmanufacturing are needed.

For example, as the semiconductor IC industry has progressed intonanometer technology process nodes in pursuit of higher device density,higher performance, and lower costs, challenges from both fabricationand design have resulted in the development of semiconductor devicessuch as metal oxide semiconductor field effect transistors (MOSFETs).However, existing semiconductor devices and methods of fabricating thesemiconductor devices have not been entirely satisfactory in allrespects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic cross-sectional view of a semiconductor device inaccordance with various embodiments.

FIG. 2A through FIG. 2K are schematic cross-sectional views ofintermediate stages showing a method for manufacturing a semiconductordevice in accordance with various embodiments.

FIG. 3 is a flow chart of a method for manufacturing a semiconductordevice in accordance with various embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact.

Terms used herein are only used to describe the specific embodiments,which are not used to limit the claims appended herewith. For example,unless limited otherwise, the term “one” or “the” of the single form mayalso represent the plural form. The terms such as “first” and “second”are used for describing various devices, areas and layers, etc., thoughsuch terms are only used for distinguishing one device, one area or onelayer from another device, another area or another layer. Therefore, thefirst area can also be referred to as the second area without departingfrom the spirit of the claimed subject matter, and the others arededuced by analogy. In addition, the present disclosure may repeatreference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed. As used herein, the term “and/or” includes anyand all combinations of one or more of the associated listed items.

In a typical method for manufacturing a semiconductor device, after aninterlayer dielectric layer is formed to cover dummy gate structures andto fill between the dummy gate structures, a chemical mechanicalpolishing (CMP) process is performed to remove an excess portion of theinterlayer dielectric layer to expose tops of dummy gate electrodes ofthe dummy gate structures. Next, the dummy gate electrodes are removedby using an etching process to form cavities, and gate electrodes arerespectively formed in the cavities for replacing the dummy gateelectrodes. However, the etching process may damage the interlayerdielectric layer. In addition, after the chemical mechanical polishingprocess and the etching process are performed, process byproducts orcontaminants remain on the interlayer dielectric layer, and the processbyproducts or the contaminants flow into the cavities during asubsequent wet clean operation, thus contaminating the cavities and thegate electrodes. Consequently, a yield of the process is reduced, andreliability of the semiconductor device is lowered.

Embodiments of the present disclosure are directed to providing asemiconductor device and a method for manufacturing the semiconductordevice, in which before an operation of replacing dummy gate electrodeswith gate electrodes, an interface layer is formed to cover dummy gatestructures and an interlayer dielectric layer. The interface layer isharder to be removed than the interlayer dielectric layer, and theinterface layer has a CMP selectivity with respect to the gateelectrodes, such that the interface layer can protect the interlayerdielectric layer during the operation of replacing the dummy gateelectrodes, and can prevent contaminants generated in an implantoperation, a CMP operation and/or an etching operation fromcontaminating the gate electrodes. Furthermore, because the interfacelayer has a CMP selectivity with respect to the gate electrodes, abetter control on the height of the gate structures can be achieved.

FIG. 1 is schematic cross-sectional view of a semiconductor device inaccordance with various embodiments. In some embodiments, asemiconductor device 100 is a MOSFET. As shown in FIG. 1, thesemiconductor device 100 includes a substrate 102, at least two gatestructures, an interlayer dielectric layer 108 and a material layer 110.For example, the semiconductor device 100 includes two gate structures104 and 106. The substrate 102 is a semiconductor substrate, and may becomposed of a single-crystalline semiconductor material or a compoundsemiconductor material. For example, the substrate 102 is a siliconsubstrate. In some examples, germanium or glass may also be used as amaterial of the substrate 102.

In some examples, at least one isolation structure 112 is disposed inthe substrate 102 to define at least two device regions in the substrate102, such as two device regions 114 and 116. For example, the isolationstructure 112 may be a shallow trench isolation (STI) structure. Theisolation structure 112 may be formed from silicon oxide. Referring toFIG. 1 again, the semiconductor device 100 further includes two dopedregions 118 and two doped regions 120 disposed in the substrate 102. Thedoped regions 118 are disposed in the device region 114, and the dopedregions 120 are disposed in the device region 116. The doped regions 118and 120 are formed by implanting dopants into the substrate 102. Theconductivity types of the dopants of the doped regions 118 and 120 aredifferent from each other. For example, the conductivity type of thedoped regions 118 may be p type or n type, while the conductivity typeof the doped regions 120 may be the other conductivity type. When thedoped regions 118 or 120 are of n type, phosphorous (P) may be used asthe dopants. When the doped regions 118 or 120 are of p type, germanium(Ge) may be used as the dopants.

The gate structures 104 and 106 are respectively disposed in the deviceregions 114 and 116 on the substrate 102. In the device region 114, thedoped regions 118 are respectively disposed at two opposite sides of thegate structure 104. One of the doped regions 118 may be a source region,and the other of the doped regions 118 may be a drain region. In thedevice region 116, the doped regions 120 are respectively disposed attwo opposite sides of the gate structure 106. One of the doped regions120 may be a source region, and the other of the doped regions 120 maybe a drain region. In some examples, the gate structure 104 includes agate dielectric layer 104 a and a gate electrode 104 b, in which thegate dielectric layer 104 a is disposed on the substrate 102, and thegate electrode 104 b is disposed on the gate dielectric layer 104 a. Thegate structure 106 includes a gate dielectric layer 106 a and a gateelectrode 106 b, in which the gate dielectric layer 106 a is disposed onthe substrate 102, and the gate electrode 106 b is disposed on the gatedielectric layer 106 a. In some exemplary examples, the gate dielectriclayers 104 a and 106 a are formed from silicon oxide, and the gateelectrodes 104 b and 106 b are formed from metal.

In some examples, as shown in FIG. 1, the semiconductor device 100further includes two spacers 122 and 124. The spacer 122 peripherallysurrounds the gate structure 104, and the spacer 124 peripherallysurrounds the gate structure 106. The spacers 122 and 124 are formedfrom dielectric materials.

In some examples, as shown in FIG. 1, according to process requirements,the semiconductor device 100 may further include an etching stop layer(ESL) 126. The etching stop layer 126 covers the substrate 102, theisolation structure 112, the doped regions 118 and 120, and the spacers122 and 124. The etching stop layer 126 may be a contact etching stoplayer (CESL) for fabricating contacts.

The interlayer dielectric layer 108 is disposed on the etching stoplayer 126 to cover the substrate 102 and the gate structures 104 and106. As shown in FIG. 1, the interlayer dielectric layer 108peripherally surrounds the spacers 122 and 124, such that the interlayerdielectric layer 108 peripherally surrounds the gate structures 104 and106. A material forming the interlayer dielectric layer 108 is differentfrom a material forming the etching stop layer 126. In some exemplaryexamples, the interlayer dielectric layer 108 is formed from flowableoxide. For example, the interlayer dielectric layer 108 may be formedfrom silicon dioxide. A top 128 of the interlayer dielectric layer 108has at least one concave 130 which may be formed during an operation offorming the interlayer dielectric layer 108 and/or an operation ofremoving an interface layer covering the interlayer dielectric layer108.

Referring to FIG. 1 again, the material layer 110 fills the concave 130.A material forming the interlayer dielectric layer 108 is different froma material forming the material layer 110. For example, the materiallayer 110 may be formed from a dielectric material or metal. In someexamples, the material layer 110 has a top surface 132 which is elevatedat the same level with top surfaces 134 a and 134 b of the gatestructures 104 and 106. In some exemplary examples, a ratio of athickness 136 of a thickest portion of the material layer 110 to a pitch138 of the gate structures 104 and 106 ranges from about 1/30 to about1/80. For example, a ratio of the thickness 136 of the thickest portionof the material layer 110 to a thickness 140 of a thickest portion ofthe interlayer dielectric layer 108 may be greater than 0 and smallerthan about 1/30.

FIG. 2A through FIG. 2K are schematic cross-sectional views ofintermediate stages showing a method for manufacturing a semiconductordevice in accordance with various embodiments. As shown in FIG. 2A, asubstrate 200 is provided. The substrate 200 is a semiconductorsubstrate, and may be composed of a single-crystalline semiconductormaterial or a compound semiconductor material. In some examples,silicon, germanium or glass may be used as a material of the substrate200.

Referring to FIG. 2A again, at least one isolation structure 202 isformed in the substrate 200 to define at least two device regions 204and 206 in the substrate 200, in which the device regions 204 and 206are separated by the isolation structure 202. In some examples, theisolation structure 202 is a shallow trench isolation structure. Forexample, the operation of forming the isolation structure 202 mayinclude forming a trench 208 in the substrate 200 by using aphotolithography technique and an etching technique, depositing anisolation material layer to fill the trench 206 by using a plasmaenhanced chemical vapor deposition (PECVD) technique, and removing anexcessive portion of the isolation material layer by using a CMPtechnique.

As shown in FIG. 2B, two dummy gate structures 210 and 212 are formed inthe device regions 204 and 206 on the substrate 200 respectively. Thedummy gate structure 210 includes a dummy gate electrode 210 b, and thedummy gate structure 212 includes a dummy gate electrode 212 b. In someexamples, the dummy gate structure 210 further includes a gatedielectric layer 210 a, and the dummy gate structure 212 furtherincludes a gate dielectric layer 212 a. In the dummy gate structure 210,the gate dielectric layer 210 a is disposed on the substrate 200, andthe dummy gate electrode 210 b is disposed on the gate dielectric layer210 a. In the dummy gate structure 212, the gate dielectric layer 212 ais disposed on the substrate 200, and the dummy gate electrode 212 b isdisposed on the gate dielectric layer 212 a. In some exemplary examples,the gate dielectric layers 210 a and 212 a are formed from siliconoxide, and the dummy gate electrodes 210 b and 212 b are formed frompolysilicon.

In some exemplary examples, as shown in FIG. 2B, after the operation offorming the dummy gate structures 210 and 212 is performed, two spacers214 and 216 are formed on sidewalls of the dummy gate structures 210 and212 respectively. The spacers 214 and 216 are formed to peripherallysurround the dummy gate structures 210 and 212 respectively. In someexemplary examples, in the operation of forming the spacers 214 and 216,a spacer material layer is firstly formed to cover the substrate 200,the isolation structure 202, and the dummy gate structures 210 and 212.Then, an etching process is performed on the spacer material layer toremove a portion of the spacer material layer to expose a portion of thesubstrate 200, so as to form the spacers 214 and 216 respectively on thesidewalls of the dummy gate structures 210 and 212.

As shown in FIG. 2C, various doped regions 218 a, 218 b, 220 a and 220 bare formed in the substrate 202. The doped regions 218 a, 218 b, 220 aand 220 b are formed by implanting dopants into the substrate 200. Thedoped regions 218 a and 218 b are formed at two opposite sides of thedummy gate structure 210 respectively, in which the doped region 218 amay be a source region, and the doped region 218 b may be a drainregion. The doped regions 220 a and 220 b are formed at two oppositesides of the dummy gate structure 212 respectively, in which the dopedregion 220 a may be a source region, and the doped region 220 b may be adrain region. A conductivity type of the doped regions 218 a and 218 bmay be different from that of the doped regions 220 a and 220 b. In someexamples, the conductivity type of the doped regions 218 a and 218 b isp type or n type, while the conductivity type of the doped regions 220 aand 220 b is the other conductivity type. For example, when the dopedregions 218 a and 218 b or the doped regions 220 a and 220 b are of ntype, phosphorous may be used as the dopants. When the doped regions 218a and 218 b or the doped regions 220 a and 220 b are of p type,germanium may be used as the dopants.

According to process requirements, as shown in FIG. 2D, after theoperation of forming the doped regions 218 a, 218 b, 220 a and 220 b iscompleted, an etching stop layer 222 may be formed to conformally coverthe substrate 200, the isolation structure 202, the doped regions 218 a,218 b, 220 a and 220 b, the spacers 214 and 216, and the dummy gatestructures 210 and 212. The etching stop layer 222 may be a contactetching stop layer for fabricating contacts. The etching stop layer 222may be formed by a deposition technique, such as a chemical vapordeposition technique.

As shown in FIG. 2E, an interlayer dielectric material layer 224 isformed on the etching stop layer 222 to cover the substrate 200 and thedummy gate structures 210 and 212. A material forming the interlayerdielectric material layer 224 is different from a material forming theetching stop layer 222. In some exemplary examples, the interlayerdielectric material layer 224 is formed by using flowable oxide. Forexample, the interlayer dielectric material layer 224 may be formed fromsilicon dioxide.

As shown in FIG. 2F, a planarization step is performed on the interlayerdielectric material layer 224 to remove a portion of the interlayerdielectric layer 224 and a portion of the etching stop layer 222 whichis overlying a top 228 of the dummy gate electrode 210 b and a top 230of the dummy gate electrode 212 b, so as to form an interlayerdielectric layer 226 and expose the tops 228 and 230 of the dummy gateelectrodes 210 b and 212 b. The interlayer dielectric layer 226peripherally surrounds the spacers 214 and 216, such that the interlayerdielectric layer 226 peripherally surrounds the dummy gate structures210 and 212. In some examples, the planarization step is performed byusing a CMP technique. In some exemplary examples, a top 232 of theinterlayer dielectric layer 226 has at least one concave 234 after theplanarization step is performed.

As shown in FIG. 2G, an interface layer 236 is formed on the interlayerdielectric layer 226 and the dummy gate structures 210 and 212. Amaterial forming the interface layer 236 is different from that formingthe interlayer dielectric layer 226. In some examples, the interfacelayer 236 is formed from silicon dioxide, silicon nitride or siliconoxynitride. The interface layer 236 is harder to be removed than theinterlayer dielectric layer 226. For example, the operation of formingthe interface layer 236 may be performed using a deposition process, animplant process, a plasma treatment process or an oxidization process.In the examples that the interface layer 236 is formed using thedeposition process, a selective atomic layer deposition (ALD) processmay be used to form the interface layer 236. In the examples that theinterface layer 236 is formed using the implant process, the implantprocess may be performed with a high dose concentration and shallowdepth. In the examples that the interface layer 236 is formed using theplasma treatment process, the plasma treatment process may be performedusing nitrogen (N₂) as a working gas. In the examples that the interfacelayer 236 is formed using the oxidization process, the oxidizationprocess may be performed using hydrogen peroxide (H₂O₂), tartaric acid(C₄H₆O₆) or citric acid (C₆H₈O₇) as an oxidant.

As shown in FIG. 2H, openings 238 and 240 are formed in the interfacelayer 236 to expose the top 228 of the dummy gate electrode 210 b andthe top 230 of the dummy gate electrode 212 b. In some examples, theoperation of forming the openings 238 and 240 is performed by using aphotolithography technique and an etching technique, such as a dryetching technique.

After the operation of forming the openings 238 and 240 is completed,the dummy gate electrodes 210 b and 212 b are replaced with two gateelectrodes 246 and 248 to complete the fabrication of gate structures250 and 252, as shown in FIG. 2J. The gate structure 250 includes thegate dielectric layer 210 a and the gate electrode 246 on the gatedielectric layer 210 a, and the gate structure 252 includes the gatedielectric layer 212 a and the gate electrode 248 on the gate dielectriclayer 212 a. In some examples, the operation of replacing the dummy gateelectrodes 210 b and 212 b with the gate electrodes 246 and 248 includesremoving the dummy gate electrodes 210 b and 212 b respectively throughthe openings 238 and 240 by using, for example, an etching technique.The operation of removing the dummy gate electrodes 210 b and 212 b maybe performed using a dry etching technique and/or a wet etchingtechnique. As shown in FIG. 2I, after the dummy gate electrodes 210 band 212 b are removed, cavities 242 and 244 are formed in the interlayerdielectric layer 226, in which the cavities 242 and 244 respectivelyexpose the gate dielectric layers 210 a and 212 a.

After the dummy gate electrodes 210 b and 212 b are removed, a gatematerial layer (not shown) is formed to fill the cavities 242 and 244and to cover the interface layer 236. The gate material layer may have aCMP selectivity with respect to the interface layer 236. The gatematerial layer may be formed from metal, such as tungsten (W). Next, aCMP process is performed on the gate material layer to remove a portionof the gate material layer overlying the interface layer 236, so as toform the gate electrodes 246 and 248 in the cavities 242 and 244 andexpose the interface layer 236.

The interface layer 236 is harder to be removed than the interlayerdielectric layer 226, and the interface layer 236 has a CMP selectivitywith respect to the gate electrodes 246 and 248, such that theinterlayer dielectric layer 226 is protected by the interface layer 236during the operation of removing the dummy gate electrodes 210 b and 212b and the CMP process, thereby preventing contaminants generated in theimplant operation, the CMP process and/or the etching operation fromcontaminating the gate electrodes 246 and 248. Moreover, the interfacelayer 236 has a CMP selectivity with respect to the gate electrodes 246and 248, and thus a better control on the height of the gate structures250 and 252 can be achieved.

In some examples, after the operation of replacing the dummy gateelectrodes 210 b and 212 b is completed, the interface layer 236 isremoved to expose the top 232 of the interlayer dielectric layer 226.For example, the interface layer 236 may be removed by using an etchingtechnique. Then, as shown in FIG. 2K, a material layer 258 is formed onthe top 232 of the interlayer dielectric layer 226 and fills the concave234 to complete the fabrication of a semiconductor device 260. Theoperation of forming the material layer 258 may include depositing thematerial layer 258 and planarizing the material layer 258. Thus, a topsurface 262 of the material layer 258 is a flat surface. In someexemplary examples, the top surface 262 of the material layer 258 iselevated at the same level with a top 254 of the gate electrode 246 anda top 256 of the gate electrode 248.

Referring to FIG. 2I through FIG. 2K again, the interlayer dielectriclayer 226 is protected by the interface layer 236 during the operationof replacing the dummy gate electrodes 210 b, such that a depth of theconcave 234 on the top 232 of the interlayer dielectric layer 226 is notincreased. Thus, a ratio of a thickness 266 of a thickest portion of thematerial layer 258 to a pitch 264 of the gate electrodes 246 and 248 mayrange from about 1/30 to about 1/80. For example, a ratio of thethickness 266 of the thickest portion of the material layer 258 to athickness 268 of a thickest portion of the interlayer dielectric layer226 may be greater than 0 and smaller than about 1/30.

Referring to FIG. 3 with FIG. 2A through FIG. 2K, FIG. 3 is a flow chartof a method for manufacturing a semiconductor device in accordance withvarious embodiments. The method begins at operation 300, where asubstrate 200 is provided. In the operation of providing the substrate200, as shown in FIG. 2A, at least one isolation structure 202 is formedin the substrate 200 to define at least two device regions 204 and 206in the substrate 200. The device regions 204 and 206 are separated bythe isolation structure 202. The isolation structure 202 may be ashallow trench isolation structure. For example, the operation offorming the isolation structure 202 may include forming a trench 208 inthe substrate 200 by using a photolithography technique and an etchingtechnique, depositing an isolation material layer to fill the trench 206by using PECVD technique, and removing an excessive portion of theisolation material layer by using a CMP technique to form the isolationstructure 202.

At operation 302, as shown in FIG. 2B, two dummy gate structures 210 and212 are formed in the device regions 204 and 206 on the substrate 200respectively. The dummy gate structure 210 includes a dummy gateelectrode 210 b, and the dummy gate structure 212 includes a dummy gateelectrode 212 b. In some examples, the dummy gate structure 210 furtherincludes a gate dielectric layer 210 a disposed on the substrate 200 andunderlying the dummy gate electrode 210 b, and the dummy gate structure212 further includes a gate dielectric layer 212 a disposed on thesubstrate 200 and underlying the dummy gate electrode 212 b. The gatedielectric layers 210 a and 212 a may be formed from silicon oxide, andthe dummy gate electrodes 210 b and 212 b may be formed frompolysilicon.

In some exemplary examples, as shown in FIG. 2B, after the dummy gatestructures 210 and 212 are formed, two spacers 214 and 216 are formed onsidewalls of the dummy gate structures 210 and 212 respectively. Thespacers 214 and 216 are formed to peripherally surround the dummy gatestructures 210 and 212 respectively. In some exemplary examples, in theoperation of forming the spacers 214 and 216, a spacer material layer isfirstly formed to cover the substrate 200, the isolation structure 202,and the dummy gate structures 210 and 212. Then, an etching process isperformed on the spacer material layer to remove a portion of the spacermaterial layer to expose a portion of the substrate 200, so as to formthe spacers 214 and 216.

At operation 304, as shown in FIG. 2C, various doped regions 218 a, 218b, 220 a and 220 b are formed in the substrate 202 by implanting dopantsinto the substrate 200. The doped regions 218 a and 218 b are formed attwo opposite sides of the dummy gate structure 210 respectively, inwhich the doped region 218 a may be a source region, and the dopedregion 218 b may be a drain region. The doped regions 220 a and 220 bare formed at two opposite sides of the dummy gate structure 212respectively, in which the doped region 220 a may be a source region,and the doped region 220 b may be a drain region. A conductivity type ofthe doped regions 218 a and 218 b may be different from that of thedoped regions 220 a and 220 b. For example, when the doped regions 218 aand 218 b or the doped regions 220 a and 220 b are of n type,phosphorous may be used as the dopants. When the doped regions 218 a and218 b or the doped regions 220 a and 220 b are of p type, germanium maybe used as the dopants.

In some examples, as shown in FIG. 2D, an etching stop layer 222 may beformed to conformally cover the substrate 200, the isolation structure202, the doped regions 218 a, 218 b, 220 a and 220 b, the spacers 214and 216, and the dummy gate structures 210 and 212 according to processrequirements. The etching stop layer 222 may be a contact etching stoplayer for fabricating contacts. The etching stop layer 222 may be formedby a deposition technique, such as a chemical vapor depositiontechnique.

At operation 306, as shown in FIG. 2E, an interlayer dielectric materiallayer 224 is formed on the etching stop layer 222 to cover the substrate200 and the dummy gate structures 210 and 212. A material forming theinterlayer dielectric material layer 224 is different from a materialforming the etching stop layer 222. As shown in FIG. 2F, a planarizationstep is performed on the interlayer dielectric material layer 224 toremove a portion of the interlayer dielectric layer 224 and a portion ofthe etching stop layer 222 which is overlying a top 228 of the dummygate electrode 210 b and a top 230 of the dummy gate electrode 212 b, soas to form an interlayer dielectric layer 226 and expose the tops 228and 230 of the dummy gate electrodes 210 b and 212 b. The interlayerdielectric layer 226 peripherally surrounds the dummy gate structures210 and 212. In some examples, the planarization step is performed byusing a CMP technique. In some exemplary examples, a top 232 of theinterlayer dielectric layer 226 has at least one concave 234.

At operation 308, as shown FIG. 2G, an interface layer 236 is formed onthe interlayer dielectric layer 226 and the dummy gate structures 210and 212. A material forming the interface layer 236 is different fromthat forming the interlayer dielectric layer 226. The interface layer236 is harder to be removed than the interlayer dielectric layer 226.For example, the operation of forming the interface layer 236 may beperformed using a deposition process, an implant process, a plasmatreatment process or an oxidization process. In the examples that theinterface layer 236 is formed using the deposition process, a selectiveALD process may be used to form the interface layer 236. In the examplesthat the interface layer 236 is formed using the implant process, theimplant process may be performed with a high dose concentration andshallow depth. In the examples that the interface layer 236 is formedusing the plasma treatment process, the plasma treatment process may beperformed using N₂ as a working gas. In the examples that the interfacelayer 236 is formed using the oxidization process, the oxidizationprocess may be performed using hydrogen peroxide (H₂O₂), tartaric acid(C₄H₆O₆) or citric acid (C₆H₈O₇) as an oxidant.

At operation 310, as shown in FIG. 2H, openings 238 and 240 are formedin the interface layer 236 to expose the top 228 of the dummy gateelectrode 210 b and the top 230 of the dummy gate electrode 212 b byusing a photolithography technique and an etching technique, such as adry etching technique.

At operation 312, the dummy gate electrodes 210 b and 212 b are replacedwith two gate electrodes 246 and 248 to complete the fabrication of gatestructures 250 and 252, as shown in FIG. 2J. The gate structure 250includes the gate dielectric layer 210 a and the gate electrode 246 onthe gate dielectric layer 210 a, and the gate structure 252 includes thegate dielectric layer 212 a and the gate electrode 248 on the gatedielectric layer 212 a. In some examples, in the operation of replacingthe dummy gate electrodes 210 b and 212 b, the dummy gate electrodes 210b and 212 b are removed respectively through the openings 238 and 240 byusing, for example, a dry etching technique and/or a wet etchingtechnique. As shown in FIG. 2I, after the dummy gate electrodes 210 band 212 b are removed, cavities 242 and 244 are formed in the interlayerdielectric layer 226 to respectively expose the gate dielectric layers210 a and 212 a.

After the dummy gate electrodes 210 b and 212 b are removed, a gatematerial layer (not shown) is formed to fill the cavities 242 and 244and to cover the interface layer 236. The gate material layer may have aCMP selectivity with respect to the interface layer 236. The gatematerial layer may be formed from metal, such as tungsten. Next, a CMPprocess is performed on the gate material layer to remove a portion ofthe gate material layer overlying the interface layer 236, so as to formthe gate electrodes 246 and 248 in the cavities 242 and 244 and exposethe interface layer 236.

In some examples, after the gate electrodes 246 and 248 are formed, theinterface layer 236 is removed to expose the top 232 of the interlayerdielectric layer 226 by using, for example, an etching technique. Then,as shown in FIG. 2K, a material layer 258 is formed on the top 232 ofthe interlayer dielectric layer 226 and fills the concave 234 tocomplete the fabrication of a semiconductor device 260. In the operationof forming the material layer 258, the material layer 258 may bedeposited and planarized. Thus, a top surface 262 of the material layer258 is a flat surface. In some exemplary examples, the top surface 262of the material layer 258 is elevated at the same level with a top 254of the gate electrode 246 and a top 256 of the gate electrode 248.

In accordance with an embodiment, the present disclosure discloses asemiconductor device. The semiconductor device includes a substrate, twogate structures, an interlayer dielectric layer and a material layer.The substrate has at least two device regions separated by at least oneisolation structure which is disposed in the substrate, and each of thedevice regions includes two doped regions disposed in the substrate. Thegate structures are respectively disposed on the device regions. In eachof the device regions, the doped regions are respectively disposed attwo opposite sides of the gate structure. The interlayer dielectriclayer is disposed over the substrate and peripherally surrounds the gatestructures. A top of the interlayer dielectric layer has at least oneconcave. The material layer fills the at least one concave. The materiallayer has a top surface which is elevated at the same level with topsurfaces of the gate structures, and a ratio of a thickness of athickest portion of the material layer to a pitch of the gate structuresranges from about 1/30 to about 1/80.

In accordance with another embodiment, the present disclosure disclosesa method for manufacturing a semiconductor device. In this method, asubstrate is provided, in which the substrate is provided to have atleast two device regions separated by at least one isolation structurewhich is disposed in the substrate. Two dummy gate structures are formedon the device regions respectively, in which each of the dummy gatestructures includes a dummy gate electrode. Various doped regions areformed in the substrate. Each of the device regions includes two of thedoped regions disposed at two opposite sides of each of the dummy gatestructures. An interlayer dielectric layer is formed on the substrate toperipherally surround the dummy gate structures. An interface layer isformed on the interlayer dielectric layer and the dummy gate structures.A material forming the interface layer is different from a materialforming the interlayer dielectric layer. Openings are formed in theinterface layer to respectively expose tops of the dummy gateelectrodes. The dummy gate electrodes are replaced with two gateelectrodes.

In accordance with yet another embodiment, the present disclosurediscloses a method for manufacturing a semiconductor device. In thismethod, a substrate is provided. The substrate is provided to have atleast two device regions separated by at least one isolation structurewhich is disposed in the substrate. Two dummy gate structures are formedon the device regions respectively, in which each of the dummy gatestructures includes a dummy gate electrode. Two spacers are formed onthe substrate to peripherally surround the dummy gate structuresrespectively. Various doped regions are formed in the substrate. Each ofthe device regions includes two of the doped regions disposed at twoopposite sides of each of the dummy gate structures. An etching stoplayer is formed to cover the substrate, the doped regions, the spacersand the dummy gate structures. An interlayer dielectric material layeris formed to cover the etching stop layer. A planarization step isperformed on the interlayer dielectric material layer to remove aportion of the interlayer dielectric material layer and a portion of theetching stop layer to form an interlayer dielectric layer and exposetops of the dummy gate electrodes. An interface layer is formed on theinterlayer dielectric layer and the tops of the dummy gate electrodes. Amaterial forming the interface layer is different from a materialforming the interlayer dielectric layer. Openings are formed in theinterface layer to expose the tops of the dummy gate electrodes. Thedummy gate electrodes are removed to form two cavities in the interlayerdielectric layer. A gate material layer is formed to fill the cavitiesand to cover the interface layer. A chemical mechanical polishingprocess is performed on the gate material layer to remove a portion ofthe gate material layer to form two gate electrodes in the cavities andexpose the interface layer. The interface layer is removed.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A semiconductor device, comprising: a substrate,wherein the substrate has at least two device regions separated by atleast one isolation structure which is disposed in the substrate, andeach of the device regions comprises two doped regions disposed in thesubstrate; two gate structures respectively disposed on the deviceregions, wherein in each of the device regions, the doped regions arerespectively disposed at two opposite sides of the gate structure; aninterlayer dielectric layer disposed over the substrate and peripherallysurrounding the gate structures; and a material layer disposed on theinterlayer dielectric layer, wherein the material layer has a topsurface which is elevated at the same level with top surfaces of thegate structures, and a ratio of a thickness of a thickest portion of thematerial layer to a pitch of the gate structures substantially rangesfrom 1/30 to 1/80.
 2. The semiconductor device of claim 1, wherein eachof the gate structures comprises: a gate dielectric layer disposed onthe substrate; and a gate electrode disposed on the gate dielectriclayer.
 3. The semiconductor device of claim 2, wherein each of the gateelectrodes is formed from metal.
 4. The semiconductor device of claim 1,further comprising two spacers peripherally surrounding the gatestructures respectively.
 5. The semiconductor device of claim 1, whereina material forming the interlayer dielectric layer is different from amaterial forming the material layer.
 6. The semiconductor device ofclaim 5, wherein the material forming the material layer is a dielectricmaterial or metal.
 7. The semiconductor device of claim 1, wherein aratio of the thickness of the thickest portion of the material layer toa thickness of a thickest portion of the interlayer dielectric layer issubstantially greater than 0 and smaller than 1/30.
 8. A semiconductordevice, comprising: a substrate; two gate structures disposed on thesubstrate and separated from each other, wherein two doped regions arerespectively disposed at two opposite sides of each of the gatestructures; an etching stop layer covering the substrate and the dopedregions, and peripherally surrounding the gate structures; an interlayerdielectric layer disposed on the etching stop layer and peripherallysurrounding the gate structures, wherein a top of the interlayerdielectric layer has at least one concave surface; and a material layerdisposed on the at least one concave surface of the interlayerdielectric layer, wherein the material layer has a top surface which iselevated at the same level with top surfaces of the gate structures, anda ratio of a thickness of a thickest portion of the material layer to apitch of the gate structures substantially ranges from 1/30 to 1/80. 9.The semiconductor device of claim 8, wherein each of the gate structurescomprises: a gate dielectric layer disposed on the substrate; and a gateelectrode disposed on the gate dielectric layer.
 10. The semiconductordevice of claim 8, wherein a material forming the etching stop layer isdifferent from a material forming the interlayer dielectric layer. 11.The semiconductor device of claim 8, wherein the interlayer dielectriclayer is formed from flowable oxide.
 12. The semiconductor device ofclaim 8, wherein a material forming the interlayer dielectric layer isdifferent from a material forming the material layer.
 13. Thesemiconductor device of claim 12, wherein the material forming thematerial layer is a dielectric material or metal.
 14. The semiconductordevice of claim 8, wherein a ratio of the thickness of the thickestportion of the material layer to a thickness of a thickest portion ofthe interlayer dielectric layer is substantially greater than 0 andsmaller than 1/30.
 15. A semiconductor device, comprising: a substrate;two gate structures disposed on the substrate, wherein gate structuresare separated by an isolation structure which is disposed in thesubstrate, and two doped regions are respectively disposed at twoopposite sides of each of the gate structures; two spacers peripherallysurrounding the gate structures respectively; an etching stop layercovering the substrate, the isolation structure, the doped regions, andthe spacers; an interlayer dielectric layer disposed on the etching stoplayer and peripherally surrounding the gate structures; and a materiallayer disposed on the interlayer dielectric layer, wherein the materiallayer has a top surface which is elevated at the same level with topsurfaces of the gate structures, and a ratio of a thickness of athickest portion of the material layer to a pitch of the gate structuressubstantially ranges from 1/30 to 1/80.
 16. The semiconductor device ofclaim 15, wherein a material forming the etching stop layer is differentfrom a material forming the interlayer dielectric layer.
 17. Thesemiconductor device of claim 15, wherein the interlayer dielectriclayer is formed from flowable oxide.
 18. The semiconductor device ofclaim 15, wherein a material forming the interlayer dielectric layer isdifferent from a material forming the material layer.
 19. Thesemiconductor device of claim 18, wherein the material forming thematerial layer is a dielectric material or metal.
 20. The semiconductordevice of claim 15, wherein a ratio of the thickness of the thickestportion of the material layer to a thickness of a thickest portion ofthe interlayer dielectric layer is substantially greater than 0 andsmaller than 1/30.